Many large and relative complicated machines, such as milling machines, grinders, and the like, require highly-skilled operators to properly organize and execute the various machine functions necessary to the realization of satisfactory end results. In a grinder or multiaxis milling machine, care must be taken to avoid possible physical interference between working elements having catastrophe potential and to otherwise properly program the sequence of machine functions so that the particular machine produces its best performance. Accordingly, automatic sequencers have been developed to relieve the operator of some portion of the responsibility for machine function programming.
Such sequencer devices typically involve a fair amount of complicated control circuitry which must be properly interfaced with mechanical and other electrical components in the controlled machine. Accordingly, malfunctions can occur not only in the machine itself, but also in the control system, the net result being the complication and aggravation of an already difficult problem of machine malfunction diagnosis.
One approach to machine malfunction diagnosis is disclosed in U.S Pat. No. 3,719,931, issued Mar. 6, 1973, on an "Apparatus For Controlling Machine Functions". That patent discloses a sequence controller for industrial machinery, such as a grinder, and including a solid-state sequencer which operates as a logical stepping switch. The controller further comprises two programmable matrices for producing output signal combinations of selected permutations in response to sequencer inputs, one matrix being arranged to control the actual execution of machine functions and the other being arranged to produce coded inputs to a comparator thereby to indicate machine function requirements which are due. Additional means are provided to generate input signals as machine functions are actually carried out and, accordingly, the comparator produces an output signal to advance the sequence only as the requirements due are actually met. Paired lights on a control-display panel indicate the machine status during any running sequence. Accordingly an operator, in the event of a machine malfunction, may look at the paired light display to determine whether a machine requirement due has not been properly met or that some machine function has been executed in advance of its proper point in the sequence. Either way, the operator is given at least some information which is of value in diagnosing a machine malfunction.